SROA: Avoid creating a fragment expression that covers the entire variable.

Fixes PR35416.

https://bugs.llvm.org/show_bug.cgi?id=35416

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319126 91177308-0d34-0410-b5e6-96231b3b80d8

Author: adrian-prantl

lib/Transforms/Scalar/SROA.cpp

@@ -4101,6 +4101,7 @@ bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
   if (!DbgDeclares.empty()) {
     auto *Var = DbgDeclares.front()->getVariable();
     auto *Expr = DbgDeclares.front()->getExpression();
+    auto VarSize = Var->getSizeInBits();
     DIBuilder DIB(*AI.getModule(), /*AllowUnresolved*/ false);
     uint64_t AllocaSize = DL.getTypeSizeInBits(AI.getAllocatedType());
     for (auto Fragment : Fragments) {
@@ -4128,10 +4129,14 @@ bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
                  "new fragment is outside of original fragment");
           Start -= OrigFragment->OffsetInBits;
         }
-        if (auto E = DIExpression::createFragmentExpression(Expr, Start, Size))
-          FragmentExpr = *E;
-        else
-          continue;
+        // Avoid creating a fragment expression that covers the entire variable.
+        if (!VarSize || *VarSize != Size) {
+          if (auto E =
+                  DIExpression::createFragmentExpression(Expr, Start, Size))
+            FragmentExpr = *E;
+          else
+            continue;
+        }
       }
 
       // Remove any existing intrinsics describing the same alloca.

test/DebugInfo/Generic/sroa-samesize.ll

@@ -0,0 +1,114 @@
+; RUN: opt -sroa -S -o - %s | FileCheck %s
+; Generated from clang -c  -O2 -g -target x86_64-pc-windows-msvc
+; struct A { double x1[]; };
+; struct x2 {
+;   x2(int) : x3() {}
+;   int x3;
+; };
+; int x4();
+; x2 x5() {
+;   x2 a(x4());
+;   return a;
+; }
+; void *operator new(size_t, void *);
+; struct B {
+;   B() { new (x8.x1) x2(x5()); }
+;   A x8;
+; };
+; void x9() { B(); }
+source_filename = "t.cpp"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.11.0"
+
+%struct.B = type { %struct.A }
+%struct.A = type { [0 x double], [8 x i8] }
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
+
+declare i32 @"\01?x4@@YAHXZ"() local_unnamed_addr
+
+define void @"\01?x9@@YAXXZ"() local_unnamed_addr !dbg !8 {
+entry:
+  %agg.tmp.ensured = alloca %struct.B, align 8
+  call void @llvm.dbg.declare(metadata %struct.B* %agg.tmp.ensured, metadata !11, metadata !DIExpression()), !dbg !24
+  %call.i.i = call i32 @"\01?x4@@YAHXZ"(), !dbg !46, !noalias !47
+  %x3.i.i.i = bitcast %struct.B* %agg.tmp.ensured to i32*, !dbg !50
+  store i32 0, i32* %x3.i.i.i, align 4, !dbg !50, !tbaa !57, !alias.scope !47
+  ; CHECK: call void @llvm.dbg.value(metadata i32 0, metadata ![[A:.*]], metadata !DIExpression())
+  ; CHECK: ![[A]] = !DILocalVariable(name: "a",
+  ret void, !dbg !62
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #0
+
+attributes #0 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 (trunk 319058) (llvm/trunk 319066)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "t.cpp", directory: "/")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 6.0.0 (trunk 319058) (llvm/trunk 319066)"}
+!8 = distinct !DISubprogram(name: "x9", linkageName: "\01?x9@@YAXXZ", scope: !1, file: !1, line: 16, type: !9, isLocal: false, isDefinition: true, scopeLine: 16, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !DILocalVariable(name: "a", scope: !12, file: !1, line: 8, type: !15)
+!12 = distinct !DISubprogram(name: "x5", linkageName: "\01?x5@@YA?AUx2@@XZ", scope: !1, file: !1, line: 7, type: !13, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !23)
+!13 = !DISubroutineType(types: !14)
+!14 = !{!15}
+!15 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "x2", file: !1, line: 2, size: 32, elements: !16, identifier: ".?AUx2@@")
+!16 = !{!17, !19}
+!17 = !DIDerivedType(tag: DW_TAG_member, name: "x3", scope: !15, file: !1, line: 4, baseType: !18, size: 32)
+!18 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!19 = !DISubprogram(name: "x2", scope: !15, file: !1, line: 3, type: !20, isLocal: false, isDefinition: false, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true)
+!20 = !DISubroutineType(types: !21)
+!21 = !{null, !22, !18}
+!22 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!23 = !{!11}
+!24 = !DILocation(line: 8, column: 6, scope: !12, inlinedAt: !25)
+!25 = distinct !DILocation(line: 13, column: 24, scope: !26, inlinedAt: !45)
+!26 = distinct !DILexicalBlock(scope: !27, file: !1, line: 13, column: 7)
+!27 = distinct !DISubprogram(name: "B", linkageName: "\01??0B@@QEAA@XZ", scope: !28, file: !1, line: 13, type: !39, isLocal: false, isDefinition: true, scopeLine: 13, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !38, variables: !42)
+!28 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "B", file: !1, line: 12, size: 64, elements: !29, identifier: ".?AUB@@")
+!29 = !{!30, !38}
+!30 = !DIDerivedType(tag: DW_TAG_member, name: "x8", scope: !28, file: !1, line: 14, baseType: !31, size: 64)
+!31 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "A", file: !1, line: 1, size: 64, elements: !32, identifier: ".?AUA@@")
+!32 = !{!33}
+!33 = !DIDerivedType(tag: DW_TAG_member, name: "x1", scope: !31, file: !1, line: 1, baseType: !34)
+!34 = !DICompositeType(tag: DW_TAG_array_type, baseType: !35, elements: !36)
+!35 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)
+!36 = !{!37}
+!37 = !DISubrange(count: -1)
+!38 = !DISubprogram(name: "B", scope: !28, file: !1, line: 13, type: !39, isLocal: false, isDefinition: false, scopeLine: 13, flags: DIFlagPrototyped, isOptimized: true)
+!39 = !DISubroutineType(types: !40)
+!40 = !{null, !41}
+!41 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !28, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!42 = !{!43}
+!43 = !DILocalVariable(name: "this", arg: 1, scope: !27, type: !44, flags: DIFlagArtificial | DIFlagObjectPointer)
+!44 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !28, size: 64)
+!45 = distinct !DILocation(line: 16, column: 13, scope: !8)
+!46 = !DILocation(line: 8, column: 8, scope: !12, inlinedAt: !25)
+!47 = !{!48}
+!48 = distinct !{!48, !49, !"\01?x5@@YA?AUx2@@XZ: %agg.result"}
+!49 = distinct !{!49, !"\01?x5@@YA?AUx2@@XZ"}
+!50 = !DILocation(line: 3, column: 13, scope: !51, inlinedAt: !56)
+!51 = distinct !DISubprogram(name: "x2", linkageName: "\01??0x2@@QEAA@H@Z", scope: !15, file: !1, line: 3, type: !20, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !19, variables: !52)
+!52 = !{!53, !54}
+!53 = !DILocalVariable(arg: 2, scope: !51, file: !1, line: 3, type: !18)
+!54 = !DILocalVariable(name: "this", arg: 1, scope: !51, type: !55, flags: DIFlagArtificial | DIFlagObjectPointer)
+!55 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64)
+!56 = distinct !DILocation(line: 8, column: 6, scope: !12, inlinedAt: !25)
+!57 = !{!58, !59, i64 0}
+!58 = !{!"?AUx2@@", !59, i64 0}
+!59 = !{!"int", !60, i64 0}
+!60 = !{!"omnipotent char", !61, i64 0}
+!61 = !{!"Simple C++ TBAA"}
+!62 = !DILocation(line: 16, column: 18, scope: !8)